Area and power consumption trade-off for Σ-Δ decimation filter in mixed signal wearable IC

Area and Power consumption are important design metrics in integrated circuit (IC), in particular in those targeted for wearable devices. Σ-Δ Analog to Digital Converter (ADC) are increasing in popularity in those devices thanks to the low bandwidth of a great number of sensors that permits to increase converter performances by the oversampling and noise shaping techniques. One of the most important part of the Σ-Δ ADC is the decimation filter, usually implemented as a Cascaded - Integrator - Comb (CIC). The various CIC architectures, in particular the Recursive and Non recursive - Polyphase ones, are well known in literature. However, filters on-chip performances are strictly related to the effective implementations. The aim of this paper is to evaluate the two architectures, with different values of the characteristic parameters, optimizing the -180 nm CMOS Standard Cell technology - design for a reduced area occupation or power consumption. Results prove that polyphase implementations, differently from theoretical analysis, are generally more power efficient than the recursive one only in a clock gated design, even with a higher area occupation. In addition, an estimation of the power consumption is provided using least squares regression.